1. Field of the Invention
This invention relates to an electro-luminescence display (ELD), and more particularly to an electro-luminescence display panel and a driving method thereof that are adaptive for increasing a light-emitting time of a pixel as well as reducing power consumption.
2. Description of the Related Art
Recently, there have been highlighted various flat panel display devices reduced in weight and bulk that is capable of eliminating disadvantages of a cathode ray tube (CRT). Such flat panel display devices include a liquid crystal display (LCD), a field emission display (FED), a plasma display panel (PDP) and an electro-luminescence (EL) display panel, etc.
The EL display panel of these display devices is a self-luminous device capable of light-emitting a phosphorous material by a re-combination of electrons with holes. The EL display panel is largely classified into an inorganic EL device using an inorganic compound as the phosphorous material and an organic EL device using an organic compound as it. Since such an EL display panel has many advantages of a low-voltage driving, a self-luminescence, a thin film type, a wide viewing angle, a fast response speed, and a high contrast, etc., it has been expected as a post-generation display device.
Generally, as shown in FIG. 1, the organic EL device is comprised of an electron injection layer 4, an electron carrier layer 6, a light-emitting layer 8, a hole carrier layer 10 and a hole injection layer 12 that are sequentially disposed between a cathode 2 and an anode 14. In such an organic EL device, if a desired voltage is applied between the cathode 2 and the anode 14, electrons generated from the cathode 2 are moved, via the electron injection layer 4 and the electron carrier layer 6, into the light-emitting layer 8 while holes generated from the anode 14 are moved, via the hole injection layer 12 and the hole carrier layer 10, into the light-emitting layer 8. Thus, the light-emitting layer 8 emits a light by a re-combination of electrons and holes fed from the electron carrier layer 6 and the hole carrier layer 10, respectively.
FIG. 2 equivalently represents a general passive matrix type EL display panel having organic EL devices arranged in a matrix pattern.
Referring to FIG. 2, the EL display panel includes a pixel matrix 20 having EL cells 26 provided for each intersection area between scan lines SL1 to SLm and data lines DL1 to DLn, a scan driver 22 for driving the scan lines SL1 to SLm, and a data driver 24 for driving the data lines DL1 to DLn.
Each of EL cells 26 can be expressed as a diode provided at the intersection area between the data line DL and the scan line SL. If a negative scanning pulse is applied to the scan line as the cathode while a positive data signal is applied to the data line DL as the anode to thereby load a forward voltage, then each of the EL cells 26 is emitted to generate a light corresponding to the data signal.
The scan driver 22 sequentially applies scanning pulses to the m scan lines SL1 to SLm.
The data driver 24 applies data signals to the m data lines DL1 to DLn in synchronization with the scanning pulses. At this time, the data driver 24 converts digital data inputted from the exterior thereof into analog data signals. More specifically, the data driver 24 voltage-divides a gamma reference voltage inputted from the exterior thereof into a plurality of gamma voltage levels, and selects the gamma voltage level corresponding to the input digital data to apply it as an analog data signal. In other words, the data driver 24 applies analog data signals having a different voltage level, that is, amplitude in accordance with digital data to each data line DL1 to DLn.
Referring to FIG. 3, the scan driver 22 sequentially applies a negative scanning pulse to the (i−1) th to (i+1)th scan lines SLi−1 to SLi+1. The data driver 24 applies the corresponding data signals Vdata1, Vdata2 and Vdata3 to the ith data line DLi in synchronization with the scanning pulse during an enable interval of the scanning pulse. In this case, the negative scanning pulse applied to the (i−1) th to (i+1) th scan lines SLi−1 to SLi+1 has a disable interval d such that it does not overlap with a scanning pulse at the previous line. In the disable interval d of the scanning pulse, the data driver 24 supplies a ground voltage 0V to the data line DLi. Thus, since the data signals Vdata1 to Vdata3 applied to the data line DLi has to be charged from the ground voltage 0V, they have relatively long rising times t1 to t3 and relatively large swing widths.
As a result, as voltage levels of the data signals Vdata1 to Vdata3 go higher, that is, as swing widths thereof go larger, the rising times t1 to t3 thereof are more increased to reduce a light-emitting period of the EL cells to that extent, thereby causing a deterioration of light-emission efficiency. Furthermore, power consumption is increased due to the large swing widths of the data signals Vdata1 to Vdata3.